Preheat oven to 425 degrees. In a large pot of boiling salted water, cook pasta 2 minutes less than package instructions (it will be undercooked). Drain. In a small bowl, toss together panko, Parmesan, and 2 teaspoons oil.
In pot, heat 2 tablespoons oil over medium-high. Add onion, season with salt and pepper, and cook until softened, 8 minutes. Add flour and whisk to coat onion with flour. Slowly whisk in broth, then milk. Cook, stirring constantly, until sauce comes to a boil. Reduce heat and simmer, stirring frequently, until sauce is thickened, about 8 minutes. Stir in pasta, tuna, and peas and season to taste with salt and pepper.
Transfer tuna mixture to a 9-by-13-inch baking dish and top with panko mixture. Bake until sauce is bubbling and crust is golden, 17 to 20 minutes. Let cool 10 minutes before serving.
Although it was a bit more involved than I prefer on a weeknight, the end result was worth it. Best tuna casserole I've ever had.
This turned out well and I like that the ingredients are easy to have on hand. It did seem more involved than I expected and took awhile to get it into the oven. I used regular breadcrumbs but next time will try panko.. ended up being way too much breadcrumbs throughout. Would recommend topping with just half a cup.
Nice meal. Easy to make out of pantry staples. Just use what you already have at home. I used spagetti and a blend of mozzarella, cheddar and Parmesan. I think next time I will add mushrooms. Would even be nice without the tuna and more veggies. My cat loved it too!